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Designation: E2788 − 11

Standard Specification for

Use of Expanded Shale, Clay and Slate (ESCS) as a MineralComponent in the Growing Media and the Drainage Layerfor Vegetative (Green) Roof Systems1

This standard is issued under the fixed designation E2788; the number immediately following the designation indicates the year of 

original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A

superscript epsilon (´) indicates an editorial change since the last revision or reapproval.

1. Scope

1.1 This specification covers the quality and grading of the

following materials for use as a mineral component of growing

media and drainage layer for extensive and intensive vegetative

(green) roof systems. The requirements are intended to cover

only materials having normal or average gradation character-istics. Procedures covered in this specification are not intended

for evaluating the performance nutrients associated with veg-

etative (green) roof growing media Where other materials are

to be used, appropriate limits suitable to their use must be

specified.

1.2 The values stated in SI units are to be regarded as

standard. The values given in parentheses are mathematical

conversions to inch-pound units that are provided for informa-

tion only and are not considered standard.

1.3   This standard does not purport to address all of the

safety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-

 priate safety and health practices and determine the applica-

bility of regulatory limitations prior to use.

1.4  This standard offers an organized collection of informa-

tion or a series of options and does not recommend a specific

course of action. This document cannot replace education or 

experience and should be used in conjunction with professional

 judgment. Not all aspects of this guide may be applicable in all

circumstances. This ASTM standard is not intended to repre-

sent or replace the standard of care by which the adequacy of 

a given professional service must be judged, nor should this

document be applied without consideration of a project’s manyunique aspects. The word    " Standard "    in the title of this

document means only that the document has been approved 

through the ASTM consensus process.

2. Referenced Documents

2.1   ASTM Standards:2

C29/C29M Test Method for Bulk Density (“Unit Weight”)

and Voids in Aggregate

C88 Test Method for Soundness of Aggregates by Use of 

Sodium Sulfate or Magnesium SulfateC127 Test Method for Density, Relative Density (Specific

Gravity), and Absorption of Coarse Aggregate

C131 Test Method for Resistance to Degradation of Small-

Size Coarse Aggregate by Abrasion and Impact in the Los

Angeles Machine

C136 Test Method for Sieve Analysis of Fine and Coarse

Aggregates

C330 Specification for Lightweight Aggregates for Struc-

tural Concrete

C331 Specification for Lightweight Aggregates for Concrete

Masonry Units

D75 Practice for Sampling Aggregates

D4254 Test Methods for Minimum Index Density and UnitWeight of Soils and Calculation of Relative Density

D4767 Test Method for Consolidated Undrained Triaxial

Compression Test for Cohesive Soils

D5883 Guide for Use of Rotary Kiln Produced Expanded

Shale, Clay or Slate (ESCS) as a Mineral Amendment in

Topsoil Used for Landscaping and Related Purposes

D6739 Test Method for Silica—pH Value

E2114 Terminology for Sustainability Relative to the Perfor-

mance of Buildings

E2399 Test Method for Maximum Media Density for Dead

Load Analysis of Vegetative (Green) Roof Systems

3. Terminology

3.1   Definitions:

3.1.1 For terms related to Expanded Shale, Clay and Slate

(ESCS), refer to Terminology D5883.

1 This specification is under the jurisdiction of ASTM Committee   D08   on

Roofing and Waterproofing and is the direct responsibility of Subcommittee D08.24

on Sustainability.

Current edition approved Dec. 1, 2011. Published February 2012. DOI: 10.1520/ 

E2788-11.

2 For referenced ASTM standards, visit the ASTM website, www.astm.org, or

contact ASTM Customer Service at service@astm.org. For  Annual Book of ASTM 

Standards volume information, refer to the standard’s Document Summary page on

the ASTM website.

Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States

1

 

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3.1.2 For terms related to sustainability relative to the

performance of buildings, refer to Terminology E2114.

3.2  Definitions of Terms Specific to This Standard:

3.3   expanded shale, clay, and slate (ESCS), n— a

lightweight, ceramic material produced by expanding and

vitrifying select shale, clay, or slate in a rotary kiln.

3.4   extensive vegetative (green) roof system, n— a vegetative

(green) roof system that utilizes a narrow range of species

limited to herbs, grasses, mosses, and drought tolerant succu-

lents such as  sedum. These types of plants can potentially be

sustained in a shallow growing media layer usually six inches

and under with generally less maintenance than   intensive

vegetative (green) roof systems.

3.5  vegetative (green) roof system, n— assembly designed to

support vegetation growth above a waterproofed membrane.

3.6  growing media (media), n— the substrate in which plants

take hold and develop.

3.7  intensive vegetative (green) roof system, n— a vegetative

(green) roof system that utilizes a wide variety of plant species

that require a growing media greater than six inches that may

include lawns, trees, and shrubs.

3.8   saturated surface dry (SSD), n— condition after the

aggregate is immersed in water for a minimum period of 72

hours with no visable water on the exposed surfaces of the

aggregate.

3.9   sedums, n— a succulent plant known for its tolerance for

extreme conditions.

4. Materials and Manufacture

4.1 ESCS is a lightweight, ceramic material produced by

expanding and vitrifying select shale, clay or slate in a rotary

kiln. It is a highly porous and low-density material. The raw

shale, clay or slate used to produce ESCS is fired in the kiln at

temperatures exceeding 1000°C. As it exits the kiln the

material is sterile, inert, and ceramic. Some crushing may be

performed to facilitate final screening in a screening system.

ESCS is generally neutral in pH although the pH can vary

somewhat depending on the raw material and the fuel used for

processing. Test Method C29/C29M determines density (loose

unit weight). Test Method   C127   is used to determine the

absorption after soaking the material. The particle distribution

is determined with the appropriate sieves as stated in Test

Method   C136. The ESCS to be sampled in accordance with

Practice D75.

5. Requirements

5.1 The aggregates shall conform to the gradation require-

ments specified in Table 1. For the drainage layer no more than

2 % by volume of aggregate particles shall have a diameter of 

<0.075 mm (No. 200 screen). As a component in the total

growing media the aggregate shall not contribute to the final

gradation of the media having more than 5 % of particles with

a diameter <0.075 mm for the media for extensive vegetative

(green) roof plantings. No more than 20 % by volume of 

particles with a diameter <0.075 mm should be present in the

total gradation of the media for intensive vegetative (green)roof plantings.

5.2   Physical Properties— The aggregate shall conform to

the physical properties specified in Table 2.

5.3   Chemical Properties— The aggregate shall conform to

the chemical properties specified in  Table 3.

6. Keywords

6.1 drainage; ESCS; green (vegetative) roofs

TABLE 1 Gradation Requirements for ESCS (Specification C330and Test Method C331)

Sieve Specifica-

tion

Drainage Layer

% Passing

Coarse Grada-

tion

% Passing

Fine Gradation

% Passing

19 mm (3 ⁄ 4   in.) 90 – 100 100 100

12.5 mm (1 ⁄ 2   in.) 90 – 100 100 100

9.5 mm (3 ⁄ 8   in.) 20 – 100 80 – 100 100

4.75 mm (No. 4) 5 – 40 5 – 40 85 – 100

2.36 mm (No. 8) 0 – 20 0 – 20 . . .1.8 mm (No. 16) 0 – 10 0 – 10 40 – 80

0.6 mm (No. 30) . . . . . . . . .

0.3 mm (No. 50) . . . . . . 10 – 35

0.15 mm (No.

100)

. . . . . . 5 – 25

0.074 mm (No.

200)

0 – 2A 0 – 5A 0 – 20A

A The percentage of material passing 0.074 mm by volume also applies to any

components including organic matter used as an amendment to the aggregate.

TABLE 2 Physical Properties of ESCS

Physical Properties Unit Drainage Coarse Fine Test Method

Bulk Density Dry Loose lbs/cf 32 – 60 32 – 65 38 – 70 Test Method C29/C29M

Bulk Density (max. water holding capacity) lbs/cf <64.0 <68.0 <90.0 Test Method C29/C29M

Maximum Index Density SSD lbs/sf <70 <70 <78 Test Method D4254

Maximum Index Density Vol % >48.0 >40.0 >10.0 Test Method C29/C29M,

see Note 1

Air Filled Porosity Vol % >30.0 >20.0 >10.0 Test Method E2399

Maximum Water-holding Capacity Vol % . . . >12.0 >35.0 Test Method E2399

Water Permeability cm per sec >1.0 cm/s >0.1 cm/s >0.001 cm/s Test Method E2399

Angle of Internal Friction (Compacted) degree 32° – 48° 32° – 48° 32° – 40° Test Method D4767

Frost-Resistance % loss <10 % <10 % <5 % Test Method C88

Los Angeles Abrasion % loss by weight <35 % . . . . . . Test Method C131,

modified method FM 1-T096

E2788 − 11

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in this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the risk 

of infringement of such rights, are entirely their own responsibility.

This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years and 

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TABLE 3 Chemical Properties of ESCS

NOTE 1—Care must be taken to specify what Test Method C29/C29M testing procedure is to be used for ESCS fines (rodding, jigging, or shoveling).Using the shoveling procedure to determine loose bulk density may result in the sample weighing less per volume moist than it will when dry becausemoisture tends to cause bulking of the ESCS fines that creates larger air pockets in the sample.

NOTE  2—ESCS is generally used in green roof systems as the mineral component of the media or as a granular drainage material. The hydraulicconductivity of the ESCS will differ depending on type and gradation. The gradation can vary from 1.9 cm ( 3 ⁄ 4 in.) to fine sand like material. The mediamay require a blend of different sizes of ESCS with or without sand or an organic component, or both, depending on whether the application is for an

Intensive or Extensive vegetative (green) roof. Variations in the media can be obtained by adjusting the gradation of ESCS to meet the desired porosity,weight or moisture retention requirement. The main adjustment that needs to be addressed is a correction for the weight and volume relationship of ESCSfines, that is, the minus 4.75 mm (No. 4) sieve size to a similar size of sand. The oven-dry or saturated surface dry/loose unit weight tests (see Test MethodC29/C29M) can be performed to establish the weight-volume relationship.

NOTE 3—The pH values signify only the pH range for the ESCS aggregate portion of the media, the pH for the total blended media should fall betweenthe range of 5.5 to 8.5 as best suited for the plant selection.

NOTE 4—Adapted from, “Diagnosis and Improvement of Saline and Alkaline Soils,” USDA Agricultural Handbook 60, L.A. Richards (ed.), U.S. Gov.Print. Office, Washington, DC 1954.

Chemical Properties Unit Drainage Intensive Extensive Test Method

pH SI . . . 5.5 – 10.5 5.5 – 10.5   D6739,

see Note 3

Salt Content mmhos/cm <1.50 mmhos/cm <0.60 mmhos/cm <0.60 mmhos/cm Saturated Paste Proce-

dure Method,

see Note 4.

E2788 − 11

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